Chromatographic analysis



July 30, 1968 5.1.. MUNRO ETAL 3,394,582

CHROMATOGRAPHIC ANALYSIS Filed Oct. Z50. 1964 m E @v E m mY. w. mokomoTRLv o NNI-R T WUEM T WMS .f A LJR BNG. Y B jm@ s MEQ v l Nm 1mOZ U W Omw @v D v W dv? LH m vm @N SE o w mmotwz Y United States Patent O3,394,582 CHROMATOGRAPHIC ANALYSIS Bradley L. Munro, Newton J. Sellars,and George R. Harvey, Jr., Bartlesville, Okla., assignors to PhillipsPetroleum Company, a corporation of Delaware Filed Oct. 30, 1964, Ser.No. 407,805 7 Claims. (Cl. 73-23.1)

ABSTRACT or THE DISCLOSURE Normally vaporous components in a pressurizedliquid stream containing normally vaporous and normally liquidcomponents are analyzed by obtaining a liquid sample in a sample loop,passing a carrier gas through the sample loop to iiush the samplecomponents therefrom and vapor- .fizing only the normally vaporouscomponents, removing the liquid components from the stream by sorption,and then passing the vaporous components to a chromatographic analysiszone.

This invention relates to an improved method and apparatus for thechromatographic analysis of fluids. In another aspect, this inventonrelates to a method and apparatus for the chromatographic analysis of arelatively light, or more volatile, fluid fraction in the presence of arelatively heavy, or less volatile, fluid fraction.

A conventional method for the determination of theV concentration ofconstituents in a fluid mixture involves the use of a chromatographicanalyzer. In chromatography, a sample of material to be analyzed isintroduced into a column containing the selective sorbent ofpartitioning material. A carrier gas is directed into the column so asto force the sample material therethrough. The selective sorbent, orpartitioning material, tends to hold the constituents of the material.This results in the several constituents of the tluid mixture flowingthrough the column at diiierent rates of speed, depending upon theira'linities for the packing or partitioning material. The column eliiuentthus consists initially of the carrier gas alone, the individualconstituents of the fluid mixture appearing later at spaced timeintervals. A conventional method for detecting the presence andconcentration of these constituents is to compare the thermalconductivity of the column eiiiuent gas with the thermal conductivity ofthe carrier gas directed to the column.

Conventionally, in the operation of a chromatographic analyzer, thesample iiuid mixture is introduced into a chromatographic column as avapor representative of the iiuid mixture. The conventional vaporouschromatographic method of analysis cannot be applied effectively to theanalysis of relatively light constituents contained in relatively heavyliquids as heating the sample mixture to the analysis temperature,preparatory to the introduction of the sample into the column, resultsin the premature separation of the light constituents for the heavierliquid in the sample valve. Particular difficulty is encountered whenattempting to analyze vapors present in liquids maintained under highpressure.

Conventionally, in the analysis of vapors contained in liquids underhigh pressure, the liquid mixture is flashed to atmospheric pressure.The rate or volume of both ashed vapors and remaining liquid isdetermined and the vaporized portion and remaining liquid bothseparately analyzed. From these determinations, the original compositionof the sample fluid mixture is determined.

Accordingly, an object of our invention is to provide an 3,394,582Patented July 30, 1968 ice improved chromatographic method of analysisand apparatus therefor.

Another object of our invention is to provide an irnprovedchromatographic method and apparatus for the analysis of a relativelylight, or more volatile, uid fraction in the presence of a relativelyheavy, or less volatile, liquid fraction.

Another object of our invention is to provide a chromatographic methodand apparatus for the analysis of vapors maintained in a liquid underpressure.

Other objects, advantages and features of our invention will be readilyapparent to those skilled in the art from the following description, thedrawing and appended claims.

By our invention, we have provided a chromatographic method andapparatus wherein the pressure of a sample liquid is :increased and thesample liquid is introduced into a iirst chromatographic zone maintainedat an elevated temperature; the vaporous eliiuent comprising a portionof the sample liquid is passed from the first chromatographic zone to asecond chromatographic zone; the presence and concentration of theconstituents of the eiiiuent passed from the rst chromatographic zone tothe second chromatographic zone is determined by analysis of theeiiiuent from the second chromatographic zone; the .rst chromatographiczone is backflushed with a liquid; and then both the iirst and secondchromatographic zones are backiiushed 'with a gaseous stream.

In a second embodiment of our invention, a sample uid mixture comprisedat least in part of a liquid is introduced into a irst chromatographiczone maintained at an elevated temperature; the varporous eii'luentcomprising a portion of the sample mixture is passed from the firstchromatographic zone to a second chromatographic zone; the presence andconcentration of constituents present in the eliiuent passed from theiirst chromatographic zone to the second chromatographic zone isdetermined by analysis of the second chromatographic zone eiil-uent; thefirst chromatographic zone is backilushed with a liquid; and then boththe irst and second chromatographic zones are backiiushed with a gaseousstream.

The invention is applicable to the analysis of a light vaporizablefraction of a liquid mixture wherein the entire liquid mixture cannotreadily be vaporized and maintained in the vaporous state whilesubjecting the vaporized liquid to chromatographic analysis. Theinvention is particularly applicable to the analysis of normallyvaporous hydrocarbons contained within normally liquid hydrocarbonsunder elevated pressures. The invention will hereinafter be described asapplied to the analysis of relatively light readily-vaporizablehydrocarbons present in mineral seal oil at an elevated pressure. Itwill be understood by those skilled in the art that the invention is notlimited thereto, but is generally applicable to the analysis ofvaporizable fractions of a liquid mixture.

FIGURE 1 is a schematic representation of one embodiment of theinvention with valves 31 and 32 maintained in a first position.

FIGURE 2 is a schematic representation of the said irst embodiment 0four invention with 31 and 32 maintained in a second position.

FIGURE 3 is a schematic representation of said iirst embodiment of ourinvention with valves 31 and 32 maintained in a third position.

Referring to FIGURE l of the drawings, a sample mixture comprising C1C6hydrocarbons and mineral seal oil is passed via conduit means 10 to aconventional densitometer 11 and from densitometer 11 via conduit means12, and valve means 13 to a Jerguson gauge 14. Initially during theintroduction of the sample mixture into Jerguson gauge 14, valves 17 and25 are maintained in the closed position. It is understood by thoseskilled in the art that the positioning of valves ,17, and other valvemeans hereinafter described can be controlled by conventional timingmechanisms known and generally used in the art of chromatographicanalysis.

A sample mixture is introduced into Ierguson gauge 14, passed fromJertguson gauge 14 via conduit means 21, and llashed across valve 22.The sample inlet -conduit means and the Jerguson gauge 14 are cooled toprevent premature ashing of the sample mixture. After a sufficientperiod of time to insure the attainment of a representative samplewithin Ierguson gauge 14, the sample mixture within Ierguson gauge :14is blocked in by closing valves 13 anid 22. The presence of a uniformsample mixture in Ierguson gauge 14 is indicated by a constant readingon the in line densitometer 11.

The Ipressure on the sample mixture in Jerguson gauge 14 is raised sothat the sample mixture will not prematurely flash, when in a subsequentstep it is sent through a heated sample valve as hereinafter described.The pressure on the sample mixture is raised by pressuring the top ofJerguson gauge 18 with a pressure regulated gas passed via conduit means24, 19 and valve means 26 lfrom gas cylinder 23 at the elevated pressureto Jerguson gauge 18. Jerguson gauge 18 and interconnecting conduit 16is filled with mercury. Valves 17 and 25 are then opened, thus sending asample mixture at an increased pressure through conduit 27 to a samplevalve 28.

Chromatographic columns 36, 40, valves 25, 28, 30, 31, 32, detector 44and attendant conduit means are positioned within zone 55 hereinafterreferred to as the analysis zone. The pressurized sample mixture isintroduced via conduit means 27 and valve means 25 to sample valve 28.Sample valve 28 can comprise a conventional chromatographic analyzersample valve, such as the slide valve described in U.S. Patent No.2,846,121. The sample mixture is vented from valve 28 via conduit means29 and valve means 30.

A carrier gas such as helium is transmitted via conduit means 47 to amulti-port, multi-conduit valve 32. A suitable multi-port valve means isdescribed in U.S. Patent No. 3,111,849. The carrier gas is transmittedthrough valve means 32 via conduit 4S and from valve means 32 viaconduit means 49 to a multi-port, multi-conduit valve 31. Valve 31 canbe a valve means such as valve means 32. The carrier gas is transmittedfrom valve means 31 via conduit means 53 and conduit means 33 to samplevalve 28.

Sample valve 28 is maintained at an elevated temperature, said elevatedtemperature the temperature of hereinafter described chromatographiccolumn 36. As illustrate-d in FIGURE 1, the pressurized sample mixtureat an elevated temperature is injected into the carrier gas streamflowing through sample valve 28 via conduit means 33 and 34.

The carrier gas containing the sample mixture is passed via conduitmeans '34 to a chromatographic column 36 containing a suitable packingmaterial such as ire brick. Column 36 is maintained at a constantelevated temperature. The mineral seal oil liquid contained in thecarrier gas passed to column 36 is retained by the re brick packingwithin column 36.

A vaporous eluent comprising carrier gas and C1-C6 hydrocarbons ispassed via conduit means 37 to valve means 31 and from valve means 31 tochromatographic column via conduit means 38 and 39. Column 40 contains asuitable packing material capable of selectively retarding the flow ofCl-C hydrocarbons therethrough. A suitable packing material comprises 10Weight percent bis(2methoxyethyl) phthalate on Chromosorb, a packingmaterial distributed by Johns-Manville Products Corp., Celite Division,22 E. 40th St., New York, N.Y.

' The vaporous effluent from chromatographic column 40 is passed viaconduit means 41, conduit means 42 within valve means 32, and conduitmeans 43 to a conventional `detector adapted to measure a property ofthe fluid mixture directed thereto, which property is representative ofthe composition of the uid mixture. Detector 44 can advantageouslycomprise a thermal conductivity analyzer which includes a temperaturesensitive resistance element disposed in the path of fluid flow. Areference element, not shown, can be disclosed in the carrier gas llow.Suc-h a detector provides signals representative of the difference inthermal conductivity between the column eluent and the carrier gas. Thetemperature differences between the resistance elements can =be measuredby an electrical bridge circuit, such as a Wheatstone bridge, forexample. However, detector 44 lcan also be any other type of apparatusknown in the art for measuring a property of a gaseous stream.Refractometers, radiation absorption analyzers and conductivity cellsare examples of such apparatus. The effluent from detector 44 is ventedvia conduit means 46.

As illustrated in FIGURE 1, the pressure of the sample mixture wasincreased to prevent premature flashing of a portion of the sample`mixture in sample valve 28 prior to injection of sample into thecarrier gas stream. Thus, it can readily be seen that should samplevalve 28 be maintained at a temperature that would not cause flashvaporization of a portion of the sample mixture within the valve, itwould not be necessary to increase the pressure of the sample mixtureand the sample mixture could thus be introduced directly into thecarrier gas stream.

After completion of the analysis steps described in the description ofFIGURE 1, valves 31 and 32 are positioned as illustrated in FIGURE 2 andcolumns 36 and 40 are backushe-d as hereinafter described. Referring toFIG- URE 2, a liquid solvent capable of removing the mineral seal oilfrom the packing material within column 36 is passed via conduit means50 and valve means 51 to valve means 31. The particular solvent employedis one that is capable of removing that portion of the sample mixtureretained in column 36 and one that can in turn be separated from thepacking material in column 36 by a 'gaseous stream in a subsequentdrying step. Suitable solvents include the light hydrocarbons containingC-Cm carbon atoms per molecule. The liquid solvent s passed from valve31 via conduit means 37 to a downstream region of chromatographic column36 and through chromatographic column 36 in a backushing step. Thesolvent containing the mineral seal oil is removed from chromatographiccolumn 36 via conduit means 34 and vented via sample valve means 28,conduit means 33, conduit means 57 in valve means 31, and conduit means56.

Chromatographic column 40 is backushed with a gaseous stream, preferablythe carrier gas, passed via conduit means 47, conduit means 60 withinvalve means 32, and conduit means 41 to the downstream region ofchromatographic column 40. The gaseous stream is withdrawn fromchromatographic column 40 via conduit means 39 and passed to detector 44via conduit means 59 in valve means 31, conduit means 49, conduit means62 within valve means 32, conduit means 54, conduit means 61 withinvalve means 32, and conduit means 43. By backushing column 40 in the4described manner, column 40 is flushed of any Cq-ifraction retained incolumn 40.

Valves 31 and 32 are then positioned as illustrated in FIGURE 3 andcolumns 36 and 40 backflushed with a gaseous stream passed to the saidcolumns as hereinafter described. A gaseous stream, preferably thecarrier gas employed, is passed |via conduit means 47 to valve means 32and to the downstream region of chromatographic column 40 via conduitmeans 60 within valve means 32, and conduit means 41. The gaseous streamis passed from column 40 via conduit means 39, conduit means 38 withinvalve means 31 and conduit means 37 to the downstream region ofchromatographic column 36.

The gaseous stream is passed from chromatographic column 36 via conduitmeans 34, Ivalve means 28, conduit means 33, con-duit means 53 withinvalve means 31, conduit means 49, conduit means 62 within valve means32, conduit means 54, conduit means 61 within valve means 32 and conduitmeans 43 to detector 44. The gaseuos stream is withdrawn from detector44 via conduit means 46.

In the backilushed position, as illustrated in FIGURES 2 and 3, columns36 and 40 are backflushed with a gaseous stream until a stable base lineis achieved as noted by detector 44.

In a specific embodiment of the invention, chromatographic column 36 is10 inches in length and contains fire brick as a packing material andchromatographic column 40 is a 40-foot long column containing a packingmaterial comprising weight percent bis(2-methoxy ethyl) phthalate onChromosorb. Columns 36 and 40 are maintained at 104 F. A sample mixturecomprising mineral seal oil and Cl--C` hydrocarbons is introduced viaconduit means 10 to densitometer 11 at 950 p.s.i.g. The pressure of thesample mixture is elevated to 1100 p.s.i.g. by the passage of gas fromgas cylinder 23 in the previously described manner. A 2-microliterliquid sample of the sample mixture is injected by valve 28 into thecarrier gas stream. Helium is employed as the carrier gas and thebackilushing gas. n-Heptane is employed as the solvent passed to column36 in the backilushing step.

By our invention, we have provided a chromatographic method of analysiswherein a relatively light vaporizable fraction can be analyzed in thepresence of a relatively heavy involatile fraction. We have further byour invention provided an improved method for backflushing achromatographic column comprising the steps of (l) backilushing thecolumn initially with a liquid solvent, and (2) subsequentlybackflushing the column with a gaseous stream to dry the column andprepare the chromatographic column for the next analysis.

As will be evident to those skilled in the art, various modifications ofthis invention can be made, or followed, in the light of the foregoingdisclosure, without departing from the spirit or scope thereof.

We claim:

1. A method of analyzing normally vaporous components within a liquidstream maintained at a first pressure containing normally vaporous andnormally liquid components comprising:

(a) isolating a portion of said liquid stream at said first pressure;

(b) increasng the pressure of said portion to a second pressure higherthan said first pressure and sufiicient to prevent the normally vaporouscomponents therein from flashing at an increased analysis temperature;

(c) passing said portion at said second pressure to a sample zone withinan analysis zone which is maintained at an increased analysistemperature;

(d) isolating a sample of said portion at said second pressure in saidsample zone;

(e) passing a carrier gas through said sample zone at a third pressurewhich is lower than said second pressure;

(f) vaporizing said normally vaporous components in said carrier gas;

(g) removing said normally liquid components from said carrier gas;

(h) passing said carrier gas containing said vaporous components to achromatographic analysis zone.

2. The method of claim 1 wherein steps (g) and (h) comprise in sequence,passing the carrier-gas stream from step (f) through a sorption zonewherein said normally liquid components are sorbed; passing the effluentfrom said sorption zone which contains said normally vaporous componentsin the vaporous state to a chromatographic column wherein said vaporizedcomponents are sorbed; and measuring a property of the effluent fromsaid chromatographic column which is representative of the compositionof said vaporized components.

3. The method of claim 2 further comprising flushing said sorption zonewith a liquid solvent for said normally liquid components to therebyremove said normally liquid components therefrom, and backllushing saidchromatographic column with a gaseous stream.

4. The method of claim 3 further comprising backflushing said sorptionzone with a gaseous stream.

5. A chromatographic sampling apparatus comprising:

(a) a first pressure vessel means having a first end and a second end;

(b) first conduit means for introducing a pressurized liquid sample intosaid first pressure vessel means, said first conduit means communicatingwith the first end of said first pressure vessel and having a firstvalve means positioned therein;

(c) second conduit means communicating with the second end of said firstpressure vessel;

(d) sample valve means adapted to obtain a liquid sample from a liquidpassed thereto;

(e) third conduit means communicating between said rst end of said firstpressure vessel means and said sample valve means for passing yliquidsample therethrough, said third conduit means having a second valvemeans operatively positioned therein;

(f) fourth conduit means communicating with said third conduit means ata point 4between said second valve means and said first end of saidfirst pressure vessel means, said fourth conduit means having a thirdvalve means operatively positioned therein;

(g) second pressure vessel means having a first end and a second end,said second pressure vessel means having mercury therein;

(h) fifth conduit means communicating with said first end of said secondpressure means;

(i) fourth valve means connecting said fifth conduit means with saidsecond conduit means;

(j) sixth conduit means communicating with said second end of saidsecond pressure vessel and having a fifth valve means operativelypositioned therein;

(k) a pressure inducing means for increasing the fluid pressure in saidsecond pressure vessel means;

(l) seventh conduit means communicating with said pressure reducingmeans and said sixth conduit means at a point between said second end ofsaid second pressure vessel and said fifth valve means for passingpressurizing iluid therethrough;

(m) sixth valve means operatively positioned in said seventh conduitmeans.

6. The apparatus of claim 5 further comprising a liquid densitymeasuring means operatively positioned in said first conduit means, andan eighth conduit means operatively connected to said sample valve meanswith a seventh valve means operatively positioned therein.

7. The apparatus of claim 5 further comprising a first sorption columnhaving a first end and a second end containing a packing material thatselectively retards the constituents of a fluid mixture directedtherethrough, a second sorption column having a first end and a secondend containing a packing material that selectively retards theconstituents of the fluid mixture directed therethrough, means formeasuring a property of a fluid representative of the compositionthereof, a first multi-port valve means, a second multi-port valvemeans, ninth conduit means communicating between said first multi-portvalve means and the rst end of said first sorption column, said samplevalve means connected to said ninth cond-uit means and adapted tointroduce a fluid therein, tenth conduit means communicating betweensaid first multi-port valve means and the second end of said firstsorption column, eleventh conduit means communicating between said firstmulti-port valve means and the first end of said second column, twelfthconduit means communicating between the second end of said second columnand said second multi-port valve means, thirteenth conduit meansconnecting between said second multi-port valve means and said means formeasuring, fourteenth conduit means comunicating between said rst andsaid second multi-port valve means, fteenth conduit means communicatingwith said second multi-port valve means for introducing a carrier gasthereto, sixteenth conduit means communicating with said first multiportvalve means for introducing a liquid solvent thereto, and seventeenthconduit means communicating with said first multi-port valve means tovent luids therefrom.

References Cited Lichtenfels et al.: Analytical Chemistry, vol. 28, No.9, September 1956, pp. 1376-1379; copy in 73-23.1.

Porter et al.: Analytical Chemistry, vol. 31, No. 5, May 1969, pp.866-870, copy in 73-23.1.

RICHARD C. QUEISSER, Primary Examiner.

0 CHARLES A. RUEHL, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF 'CORRECTION Patent N0.3,394,582 July 30, 1968 Bradley L. Munro et al.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 6, line 4S, "reducing" should read inducing Column 7, line l,"Connecting" should read -e communicating signed e'h'd sealed this 30thdey ef December 1969.

(SEAL) Attest:

Edwardv M. Fletcher, Jr. WILLIAM E. SCHUYLER,

Attesting Officer Commissioner of Patents

